Martin Ridout

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Zero-inflated models

Zero-inflated distributions are used to model count
data that have many zero counts. For example, the zero-inflated Poisson
distribution might be used to model count data for which the proportion
of zero counts is greater than expected on the basis of the mean
of the non-zero counts.

In recent years, there has been considerable interest in regression
models based on zero-inflated distributions. Much of this interest
stems from the seminal paper of Lambert [Ref 1],
though this type of model appears to have originated in
the econometrics literature.

Clarice Demetrio,
John Hinde and I wrote a review paper on models for
count data with many zeros for the
International Biometric Conference, Capetown, December 1998 [Ref 2].
Although this review was reasonably complete at the time, there is
a substantial subsequent literature on this topic,
including one contribution of our own [Ref 3].